Flask



FIG. 1 is a perspective, top view of a flask showing my new design;

FIG. 2 is a front view thereof.

FIG. 3 is a back view thereof.

FIG. 4 is a side view thereof.

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof. 

The ornamental design for a flask, as shown and described. 